OSTERHOUT: THE NUCLEUS AS A CENTER OF OXIDATION 343 
Warburg’? found that it was possible to isolate the nuclei from 
erythrocytes of birds (by freezing and thawing) and that such nuclei 
consumed oxygen about as rapidly as the normal cells. While this 
indicates that the nucleus is the principal agent in oxidation other 
experiments of Warburg have been interpreted to indicate that oxida- 
tion is practically confined to the surface of the cell.!! In these experi- 
ments” it was found that NaOH greatly increased oxidation in the 
sea-urchin egg but did not penetrate sufficiently to cause a change of 
color in eggs stained with neutral red. In a later paper R. Lillie” 
comes to the conclusion that rapid oxidation occurs at, the surface 
of the cell as well as at the surface of the nucleus. This conclusion 
is based upon a study of the indophenol reaction in the corpuscles of 
frog’s blood. 
The use of the indophenol reaction may encounter an objection on 
the ground that the result may depend to a considerable extent on the 
manner in which the reagent penetrates. If the oxidizing substances 
of the cell are largely concentrated in the nucleus those which are 
present in the cytoplasm will first meet the reagent at the cell surface 
and may produce at that point a deposit of granules of indophenol. 
In the same manner the oxidizing substances which are retained 
within the nucleus will first meet the reagent at the surface of the 
nucleus and produce a deposit in that region. 
If, therefore, the indophenol reaction shows a higher oxidative 
activity in the nucleus it may doubtless be depended on, since its 
error presumably lies in the opposite direction. But if it indicates a 
marked oxidative activity at the surface of the cell (or at internal 
surfaces, including that of the nucleus) we must be cautious in drawing 
conclusions. 
It would seem that more reliable evidence can be obtained by 
investigating cases where it is not necessary that the reagent should 
penetrate from without owing to the fact that the cell itself produces 
substances which become colored on oxidation. 
The writer has investigated a case of this kind. The plant chosen 
was the Indian Pipe, Monotropa unifiora, which is extremely well suited 
to such investigations because the colorless cells contain a‘ chromo- 
gen which oxidizes and darkens very rapidly upon injury. An addi- 
10 Warburg, O. Zeit. f. physiol. chem. 70: 413. IQIO-II. 
This interpretation is by no means necessary. Cf. Loeb and Wasteneys, 
Jour. of Biochemistry 14: 459. 1913; 21: 153. 1915; also, Osterhout, ibid. 19: 335. 
1914. Owing to the buffer action of protoplasm and to the presence of pigment 
the penetration of a small amount of alkali is not easily detected. 
2 Warburg, O. Zeit. f. physiol. chem. 66: 305. 1910. Biochem. Zeit. 29: 
414. IgIo. 
13 Jour. of Biol. Chem. 15: 237. 1913. 
